Poly-alpha-olefins (PAOs) produced by oligomerizing alpha-olefins have many unique properties rendering them useful as lubricant base stocks. For example, PAOs typically have high viscosity indicies (VIs), low pour points and can be prepared with a range of viscosities.
Notwithstanding their generally superior properties, PAO lubricants are formulated with additives to enhance those properties for specific applications. The additives which are more commonly used in lubricants include oxidation inhibitors, rust inhibitors, metal passivators, antiwear agents, extreme pressure additives, pour point depressant, detergent-dispersants, viscosity index improvers, antifoamants and the like. However, as is known, PAOs by themselves generally have a low solvency for many additives, especially polar additives. Also, PAOs by themselves tend to have poor dispersancy for sludges generated during use. Consequently, polar base stocks such as polyester fluids are often combined with PAOs to provide solvency and dispersancy to the formulated lubricant. Addition of polar base stocks, however, can complicate preparing a fully formulated lubricant and may introduce other undesirable affects such as the hydrolytic instability associated with polyester base stocks.
Adding to the complexity of formulating lubricating oils is the trend to ever higher oil performance standards dictated by the increasing complexity of newer equipment and engines.
One object of the invention therefor is to improve the solvency of PAO base stocks. Another object of the invention is to improve the dispersancy of PAO base stocks.